1/* 2Redistribution and use in source and binary forms, with or without 3modification, are permitted provided that the following conditions are met: 4 5 * Redistributions of source code must retain the above copyright 6 notice, this list of conditions and the following disclaimer. 7 8 * Redistributions in binary form must reproduce the above copyright 9 notice, this list of conditions and the following disclaimer in the 10 documentation and/or other materials provided with the distribution. 11 12 * Neither the name of "The Computer Language Benchmarks Game" nor the 13 name of "The Computer Language Shootout Benchmarks" nor the names of 14 its contributors may be used to endorse or promote products derived 15 from this software without specific prior written permission. 16 17THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 18AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 21LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 22CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 23SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 24INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 25CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 26ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 27POSSIBILITY OF SUCH DAMAGE. 28*/ 29 30/* The Computer Language Benchmarks Game 31 * http://shootout.alioth.debian.org/ 32 * 33 * contributed by The Go Authors. 34 * based on pidigits.c (by Paolo Bonzini & Sean Bartlett, 35 * modified by Michael Mellor) 36 */ 37 38package main 39 40import ( 41 "flag" 42 "fmt" 43 "math/big" 44) 45 46var n = flag.Int("n", 27, "number of digits") 47var silent = flag.Bool("s", false, "don't print result") 48 49var ( 50 tmp1 = big.NewInt(0) 51 tmp2 = big.NewInt(0) 52 tmp3 = big.NewInt(0) 53 y2 = big.NewInt(0) 54 bigk = big.NewInt(0) 55 numer = big.NewInt(1) 56 accum = big.NewInt(0) 57 denom = big.NewInt(1) 58 ten = big.NewInt(10) 59) 60 61func extract_digit() int64 { 62 if numer.Cmp(accum) > 0 { 63 return -1 64 } 65 66 // Compute (numer * 3 + accum) / denom 67 tmp1.Lsh(numer, 1) 68 tmp1.Add(tmp1, numer) 69 tmp1.Add(tmp1, accum) 70 tmp1.DivMod(tmp1, denom, tmp2) 71 72 // Now, if (numer * 4 + accum) % denom... 73 tmp2.Add(tmp2, numer) 74 75 // ... is normalized, then the two divisions have the same result. 76 if tmp2.Cmp(denom) >= 0 { 77 return -1 78 } 79 80 return tmp1.Int64() 81} 82 83func next_term(k int64) { 84 y2.SetInt64(k*2 + 1) 85 bigk.SetInt64(k) 86 87 tmp1.Lsh(numer, 1) 88 accum.Add(accum, tmp1) 89 accum.Mul(accum, y2) 90 numer.Mul(numer, bigk) 91 denom.Mul(denom, y2) 92} 93 94func eliminate_digit(d int64) { 95 tmp3.SetInt64(d) 96 accum.Sub(accum, tmp3.Mul(denom, tmp3)) 97 accum.Mul(accum, ten) 98 numer.Mul(numer, ten) 99} 100 101func printf(s string, arg ...interface{}) { 102 if !*silent { 103 fmt.Printf(s, arg...) 104 } 105} 106 107func main() { 108 flag.Parse() 109 110 var m int // 0 <= m < 10 111 for i, k := 0, int64(0); ; { 112 d := int64(-1) 113 for d < 0 { 114 k++ 115 next_term(k) 116 d = extract_digit() 117 } 118 119 printf("%c", d+'0') 120 121 i++ 122 m = i % 10 123 if m == 0 { 124 printf("\t:%d\n", i) 125 } 126 if i >= *n { 127 break 128 } 129 eliminate_digit(d) 130 } 131 132 if m > 0 { 133 printf("%s\t:%d\n", " "[m:10], *n) 134 } 135} 136